Brief Description of Prior Art
An apparatus which produces a heated fluid by passing the fluid through a series of concentric convolutions of a coil, and providing a heater device at the bottom of these coils, is described in U.S. Pat. No. 3,811,414 to Minton. In the Minton heat exchange structure, a burner assembly is provided immediately beneath the lower central portion of a series of convoluted, concentrically arranged heat exchange coils. The fluid to be heated is charged from an entrance or charging point to the coil assembly, and through the coil assembly and to an outer steam nozzle. The coil assembly includes an outer helically wound coil, and an inner helically wound coil which is disposed radially inwardly from the outer coil. The convolutions of the inner and outer coils are radially separated so that the fluid which is passed therethrough purposes of heating is maintained at a relatively low temperature within the outer coil as compared to the temperature within the inner coil. This facilitates insulation of the coil assembly, and denhances the heat transfer efficiency of the heat exchange aparatus thus provided. The coil assembly is enclosed within a double-walled cylindrically shaped housing.